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Protein shake-up Ancient proteins could hold the key to unlocking the secrets of Australia's lost giant megafauna, a new paper suggests.

The paper highlights the work of an international team in using ancient proteins to fill in gaps of understanding that ancient DNA cannot provide, in particular the presence of diseases in ancient times.

In today's Science journal, Dr Enrico Cappellini at the University of Copenhagen's Centre for GeoGenetics, and colleagues argue ancient proteins can also allow researchers to look further back in time because DNA chains fall apart 10 times faster than proteins.

Cappellini says proteins survive for longer simply "because they are originally present in higher quantities".

He says by example, in bones — one of the most common archaeological fossil materials — 20-30 per cent of the mass is represented by soft tissue, which is mainly made of proteins, in particular collagen.

The team, which includes Curtin University Adjunct Professor Thomas Gilbert, says advances in high resolution, mass spectrometry technology provides the accuracy and robustness required for confident and reliable sequencing of ancient proteins.

Advantages

Cappellini says ancient protein has many advantages over ancient DNA in research.

"Ancient proteins can be recovered and sequenced even in samples in which the DNA is too quantitatively limited or too degraded to be useful," he says.

"Protein analysis, for example, can be useful to assign archaeological bone fragments to an certain animal species, even when these fragments are too small to be assigned on morphological basis or they come from an environment presenting harsh chemical conditions that made ancient DNA analysis impossible."

Importantly he says protein expression in an organism can be tissue-, process-, and developmental phase-specific, "while its genome is virtually identical over the entire lifespan of the same individual".

"Consequently detection of specific proteins or protein patterns in an ancient sample can allow us to identify biological processes that took place in that sample, or to identify the biological tissue of origin of a specific material of animal origin."

Cappellini points to their work published earlier this year on a human medieval mouth that showed microbial proteins acting as virulence factors responsible for triggering the infection process and host proteins involved in the immune response to the infection.

Using a similar approach the researchers were able to determine a 500-year-old Inca mummy had a severe bacterial infection at the time of its death.

Cultural information

The technique also can reveal important cultural information, suggests Cappellini.

He says in paintings, the pigment is made spreadable on the canvas by mixing it with an organic material called binder. Binders can have a lipid base (oil colours), or a protein base (tempera colours).

Identification of the origin of tempura colour binders such as collagen, egg or milk, "can be useful in cultural heritage preservation," says Cappellini.

The researchers are also using ancient proteins to gain more information about extinct species such as the woolly mammoth by using the protein sequences of modern species — in this case, the elephant — and then "try to fish out the differences distinctive for ancient samples".